feat(ui): show repo count in contribution graph summaries

Add "in N repositories" to both the year and all-time graph summary
lines. Year graph counts repos with overlapping activity; all-time
graph uses total project count. OG image includes repo count too.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/moments-api/src/main.rs

@@ -180,7 +180,10 @@ async fn og_contributions(
         .await
         .map_err(internal)?;
 
-    let png = render_contributions_png(&counts, earliest, today).map_err(|e| ApiError {
+    let projects = state.store.list_projects().await.map_err(internal)?;
+    let repo_count = projects.len();
+
+    let png = render_contributions_png(&counts, earliest, today, repo_count).map_err(|e| ApiError {
         status: StatusCode::INTERNAL_SERVER_ERROR,
         message: e,
     })?;
@@ -199,6 +202,7 @@ fn render_contributions_png(
     counts: &[DailyCount],
     from: NaiveDate,
     to: NaiveDate,
+    repo_count: usize,
 ) -> Result<Vec<u8>, String> {
     use std::collections::HashMap;
 
@@ -280,8 +284,13 @@ fn render_contributions_png(
     let mut svg = format!(
         r#"<svg xmlns="http://www.w3.org/2000/svg" width="{svg_w}" height="{svg_h}" viewBox="0 0 {svg_w} {svg_h}"><rect width="100%" height="100%" fill="{bg}"/>"#,
     );
+    let repo_text = if repo_count > 0 {
+        format!(" in {repo_count} repositories")
+    } else {
+        String::new()
+    };
     svg.push_str(&format!(
-        r##"<text x="{x}" y="18" fill="#ecf0f1" font-size="12" opacity="0.6">{total} contributions since {from}</text>"##,
+        r##"<text x="{x}" y="18" fill="#ecf0f1" font-size="12" opacity="0.6">{total} contributions since {from}{repo_text}</text>"##,
         x = year_label_w,
     ));